docs: def copy(self, from_path, to_hdfs, to_path):
          """
          Copy file from one filesystem to another.
  
          :type from_path: str
          :param from_path: the path of the source file
          :type to_hdfs: :class:`hdfs`
          :param to_hdfs: destination filesystem
          :type to_path: str
          :param to_path: the path of the destination file
          :raises: :exc:`~exceptions.IOError`
          """
          _complain_ifclosed(self.closed)
          if isinstance(to_hdfs, self.__class__):
              to_hdfs = to_hdfs.fs
          return self.fs.copy(from_path, to_hdfs, to_path)